Post on 26-Mar-2015
Measuring MotionMeasuring Motion
Words to KnowWords to Knowspeedspeed
magnitudemagnitudevelocityvelocity
accelerationacceleration
All types of motion can All types of motion can be described, measured, be described, measured,
and and even predicted.even predicted.
Rate of motion can be Rate of motion can be measured and is called measured and is called
speedspeed. . VelocityVelocity is another is another measure of motion that measure of motion that takes into consideration takes into consideration
both rate of motion (speed) both rate of motion (speed) and direction .and direction .
speed = distance/timespeed = distance/time
velocity= distance/time velocity= distance/time in a given direction in a given direction
So, if speed remains So, if speed remains constant, but direction constant, but direction
changes, then the changes, then the velocity has changed.velocity has changed.
The motion of an object The motion of an object can be described by its can be described by its position, direction of position, direction of motion, and speed.motion, and speed.
We commonly talk about travel in these terms. For example, last week I left
my house (starting position), went west
(direction) on highway 70 at 50 km/hr (speed). I arrived at the beach
(ending position) in 40 minutes.
But we can really measure ANY motion of
any object at any time by noting its position,
speed, and direction.
In addition, we can In addition, we can measure changes in an measure changes in an
object’s motion and object’s motion and position.position.
We can measure We can measure changing rates of speed changing rates of speed (called (called accelerationacceleration) and ) and we can measure changes we can measure changes
in direction.in direction.
Acceleration is the Acceleration is the measure of the measure of the
change in velocity.change in velocity.
A race car changes velocity A race car changes velocity as it goes around the track. as it goes around the track. To calculate the acceleration To calculate the acceleration
of a race car, divide the of a race car, divide the change in velocity by the change in velocity by the
time it takes the velocity to time it takes the velocity to change. change.
acceleration = (final velocity - original acceleration = (final velocity - original
velocity) / timevelocity) / time oror
a = (va = (v22 – v – v11)/t)/t
We can apply the We can apply the concepts of speed and concepts of speed and velocity to enable us to velocity to enable us to measure time intervals.measure time intervals.
Knowing the relationships of the
velocity of planets, the moon, the earth’s
rotation, etc. allow us to measure our days,
months, years, etc.
We could also measure time if we know the
speed of a vehicle and the distance traveled.
Since speed = Since speed = distance/time, distance/time, it follows that it follows that
time = distance/speedtime = distance/speed
What is the difference between speed
and velocity?
A: only speed is distance traveled over time
B: only velocity is distance traveled over time
C: both are distance traveled over time but velocity takes into account
directionD: both are distance traveled over time but speed takes into account
direction
A race car travels 500 km around a track in 3.5 hours. What is the
speed of the car?
A: 143 km/hrB: 286 km/hrC: 165 km/hr
D: not enough information in the question
An airplane travels 500 km/hour toward the southwest for 1.3
hours. How far did the plane go?
A: 385 hoursB: 650 km
C: 650 km/hr southeastD: 385 km
Which of the following is expressed as velocity?
A: 45 km/hrB: 45 km/hr southwest
C: 45 km southD: 45 hours
Which of the following is NOT a way to measure time intervals?
A: keeping track of the movement of the moon
B: knowing the speed of a vehicle and how far it traveledC: determining velocity from
distance and timeD: using a computerized
stopwatch
A race car's beginning velocity is 0 km/sec. It's velocity at the end of
the first lap is 0.06 km/sec. It takes 65 seconds to make the first
lap. What is the race car's acceleration?
A: 9.23 km/sB: 9.23 km/s/sC: 39 km/s/s
D: 39 sec
A storm becomes a hurricane as it is traveling at 17mph toward the northwest. It covers 1400 miles before being downgraded to a
tropical storm. How long was the hurricane active?
A: 82 hoursB: 8 days
C: 23,800 hoursD: 14 days
A train travels 2500 km in 17 hours. What is the train's average
speed?
A: 425 km/hrB: 147 km/hrC: 42.5 km/hr
D: none of the above
As you are traveling down main street at 30 mph, a car passes you going in the same direction. What can you tell
about the car that passed you
A: the car was traveling at 33 mphB: the car passing you was going
more than 30 mphC: the car passing you was
accelerating at a rate of 5 mph/hD: nothing - there is not enough
information
A speed boat is traveling at 65 mph south. Another is traveling at 65 mph west. What
can you tell about the boats?
A: they will meet after traveling 30 minutes
B: they have the same speed but not the same velocity
C: they have the same velocity but not the same speed
D: they have the same acceleration and the same velocity